Can cold weather cause an engine to flood?

Dear Car Talk

Dear Car Talk | May 01, 1999

Dear Tom and Ray:

Well, I'm using that old line, "I'm writing for a friend." But in this case, it's
actually true! A friend of mine recently bought a brand-new 1998 Dodge Neon.
After five months of blissful ownership, the Neon refused to start when it got
cold this winter. We live in Minnesota, so I do mean COLD. She had it towed to
the dealer, who told her that the engine was flooded and that it wasn't covered
by warranty. They charged her $100 to "unflood" the engine and change her oil,
because they said gas had gotten into the oil due to the flooding. They said that
the reason it flooded was that it was too cold for the gasoline to become an
aerosol, so it couldn't ignite. It hasn't been that cold since, but I'm just
wondering if the dealer knew what he was talking about. Or did he just take my
friend for a ride? -- Marc

RAY: Sounds pretty reasonable to us, Marc.

TOM: When all is right with the world, gasoline comes into the cylinder as a
vapor. The fuel injectors spray the gas in under high pressure. And that gasoline
"spray" or "vapor" is easy for the spark plug to ignite.

RAY: But when it's butt-freezing cold outside, as soon as that vapor hits the
cold, metal cylinder walls it condenses and turns back into a liquid.

TOM: And in liquid form, gasoline is surprisingly hard to ignite. Plus, the
liquid gasoline can actually "wet" the electrodes on the spark plugs (that's like
wetting the head of a match), and a wet electrode can't make a spark. Under these
conditions, the engine is said to be "flooded."

RAY: So if you think you've flooded your car (if it doesn't start in the first 30
seconds of cranking), stop trying to start it immediately. You'll only make it
worse by cranking it. You'll just be pouring more gas into the cylinders. That's
undoubtedly what your friend did. In fact, she dumped so much gas in there that a
lot of it leaked down past the piston rings into the crankcase. And that's what
contaminated her oil.

TOM: So once the engine is flooded, here's what you SHOULD do: Try to start it
one more time with the gas pedal held all the way to the floor. That sounds
counterintuitive, but fully depressing the gas pedal does two things. First, it
opens the throttle and lets extra air into the cylinders. Second, it sends a
signal to the car's computer that the engine is flooded. The computer then
greatly reduces the amount of gasoline sent in by the fuel injectors. So if the
engine is not flooded too badly, you may be able to get it started that way.

RAY: On the other hand, by the time you do that, it may already be too late. So
if it still doesn't start, then you simply have to wait until the spark plugs dry
out. That can take anywhere from an hour to several hours.

TOM: Or perhaps a fortnight, depending on the outside temperature and how badly
you've flooded it.

RAY: So in the future, tell your friend if the car doesn't start on the first or
second attempt, she should use the "foot-to-the-floor" method. And if that
doesn't work, she should give up, go back inside and congratulate herself on
earning an unexpected morning off from work.


Don?-t get stuck with a lemon. Order Tom and Ray's guide How to Buy a Great Used
Car: Things Detroit and Tokyo Don?-t Want You to Know by sending $3 and a stamped
(55 cents), self-addressed, No. 10 envelope to Used Car, PO Box 6420, Riverton,
NJ 08077-6420.


?(C) 1999 by Tom and Ray Magliozzi and Doug Berman
Distributed by King Features Syndicate, Inc.

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